diff --git a/module/VuFind/src/VuFind/Statistics/AbstractBase.php b/module/VuFind/src/VuFind/Statistics/AbstractBase.php
index ca6121f91ae46a3c9401d9bb21d21b8e74f5db3f..db3f5b68a93c3f234190df0cad74162af7ee6d51 100644
--- a/module/VuFind/src/VuFind/Statistics/AbstractBase.php
+++ b/module/VuFind/src/VuFind/Statistics/AbstractBase.php
@@ -43,6 +43,12 @@ abstract class AbstractBase implements ServiceLocatorAwareInterface
 {
     protected $drivers = null;
     protected $source;
+
+    /**
+     * Service locator
+     *
+     * @var ServiceLocatorInterface
+     */
     protected $serviceLocator;
 
     /**